Method and apparatus for the attenuation of heat softenable materials into fibers



D. KLEIST May 17, 1960 2,936,480 METHOD AND APPARATUS FOR THEATTENUATION OF HEAT SOFTENABLE MATERIALS INTO FIBERS 2 Sheets-Sheet 1Filed May 18, 1956 AIR STEAM 0!? GA mmvrox Da/e l1 lc-vsf RTTQRNE 71$SUCTION BOX May 17, 1960 D. KLEIST 2,936,480

METHOD AND APPARATUS FOR THE ATTENUATION OF HEAT SOFTENABLE MATERIALSINTO FIBERS Filed May 18, 1956 2 Sheets-Sheet 2 HTTOIZNE Y5 UnitedStates Patent METHOD AND APPARATUS FOR THE ATTENUA- 113g? RgF HEATSOFIENABLE MATERIALS INTO Dale Kleist, St. Louisville, Ohio, assignor toOwens- Corning Fiberglas Corporation, a corporation of DelawareApplication May 18, 1956, Serial No. 585,886

9 Claims. (Cl. 18-2.5)

This invention relates to a methodand apparatus for the attenuation ofheat softenable materials into fibers and it is particularly directed tothe formation of long, fine fibrous glass.

It is known that long, fine diameter glass fibers can be formed forutilization in insulating mats and blankets by centrifugally projectingstreams of glass into an extremely hot blast of gases moving at highvelocity.

Apparatuses and methods suitable for carrying out the just describedprocess are shown, for examples, in I-Ieymes and Peyches Patent No.2,624,912 and in Slayter and Stalego Patent No. 2,609,566. However, theuse of extremely hot blasts of gases, particularly the productsofcombustion of gas and airin a closed chamber, creates a substantialproblem from a manufacturing standpoint resulting from the volume andheat of the blast.

ltis, therefore, the principal object of this invention to provide amethod and apparatus by which large volumes of glass may be attenuatedinto fine fibers through the use of simple attenuation blasts such assteam, air, heated air, or superheated steam where it is not necessaryto have combustion take place in order to furnish the gases. While ithas been suggested in the prior art that fibers may be formed by theattenuation of blasts of steam or air, it has heretofore been difficultif not impossible to produce'fibers having diameters in the order of,say, 50 hundred thousandths of an inch or less by these methods.

It is, therefore, also an object of this invention to provide a methodand apparatus whereby a simple blast of air or steam in itself muchcooler than the material which it is employed to attenuate, may beutilized with the use of certain auxiliary or supplemental heating meansdesigned and employed to control the rate of heat loss of the materialbeing attenuated.

Other and more specific objects will be better understood from thespecification which follows and from the drawings in which:

Fig. 1 is a viewin vertical section, partially schematic in nature, ofan apparatus designed and operated according to the invention for theformation of very fine diamcter fibers from molten glass.

Fig. 2 is an enlarged, fragmentary, vertical, sectional view of amodification of apparatus built according to the invention. r Fig. 3 isa view similar to Fig. 2 but showing yet another modification of theapparatus.

Fig. 4 is a view similar to Figs. 2 and 3 but showing still anothermodification of the apparatus.

Fig. 5 is a schematic illustrationof yet another modification ofapparatus for practicing the invention.

rs the embodiment of the invention illustrated in Fig. l aglass meltingtank is generally indicated at and shown as providing a body of moltenglass 11. The tank 10 base bushing 12 with a single relatively largediameter orifice 13 through which flows a stream of molten glass 14.

A spindle generally indicated at 15 is mounted for rotation on avertical axis by suitable bearings (not shown) and may be driven, say,at 3000 r.p.m. or more, by belts 16 also engaged with a suitable drivingmotor (not shown) On the lower end of the spindle 15 there is removablysecured a centrifuge 17 shown in the form of a hollow cone shaped bodyhaving a generally vertical an-' nular periphery 18 and a return lowerlip 19. In the embodiment of Fig. 1 the centrifuge 17 carries acentrally located distributing basket 20 which rotates with thecentrifuge 17 and is centrally located therein.

The spindle 15 is hollow so that the stream of glass 14 flows downwardlythrough the spindle 15 and into the bottom of the basket or distributor2 0. The glass, still at relatively high temperature, flows across thebot tom of the distributing basket 20 and is projected by centrifugalforce radially outward through a plurality of distributing orifices 21drilled in the vertical walls of the basket 20. Glass flies away fromthe distributing basket 20 in the form of relatively heavy streams 22which impinge upon the periphery 18 and lip 19 of the centrifuge 17. Theglass on the inner surfaces of the periphery 18 and lip 19 fiowstogether to form an annular body of glass generally indicated at 23which is subjected to extremely high centrifugal forces because of therelatively large diameter of the centrifuge 17 and its relatively highspeed of rotation. The centrifugal force thus created extrudes the glassthrough a large number of stream forming orifices 24 that are drilled inthe periphery 1 8 of the centrifuge 17 The problem of control of thetemperature and thus the viscosity of the glass in its travel to theinner walls of the periphery 18 and lip 19, through the orifices 24 andsub sequently until attenuation is completed is critical. Thetemperature of the glass at the orifices 24 must be sufiiciently high sothat it will flow through the orifices 24 but sufficiently low so thatit will not separate from itself in the form of droplets or slugs. Ithas been discovered that while the temperature of the glass in itspathway from the centrifuge should continuously decrease, it isessential that its rate of heat loss be retarded under controlimmediately or shortly after it has left the orifices 24 so that it canbe successfully attenuated into long, fine fibers by the forces of thecentrifuge and of an attenuating blast generally indicated at 25 andsurrounding the periphery 18 of the centrifuge 17.

The attenuating blast 25 is emitted from an annular blower ring 26. Theblast may be air, heated air, steam, or superheated steam or any otherblast of gases having suificient velocity to apply traction to streamsof glass 27 flowing away from the orifices 24 under centrifugal force.

if an attenuating blast is employed at high enough temperatures so thatit reheats the glass beyond its refusing point, i.e., to such atemperature that the glass surfaces are softened, theintimate contactbetween the surfaces of the fibers being attenuated so scratches androughens the surfaces that the resulting product is brashy and lesssuitable for use in end products. It is desirable, therefore, not toincrease the temperature of the glass streams issuing from thecentrifuge. However, it has been discovered that the blast of gases plusthe assaaeo ambient air surrounding the centrifuge 17 so rapidly coolsthe glass streams that the attenuating lengths of the individual streamsare too short to permit attenuation to very fine fibers. For thisreason, it is also desirable to retard the rate of heat loss from theglass by supplying supplemental heat to the attenuating length of thestreams.

As used herein, the term attenuating length is defined as meaning thatlength of the stream between the outer surface of the periphery 18 ofthe centrifuge 17 and the position in the fiber where it has reached itsminimum diameter. During this attenuating length the fiber must beelongated sufficiently so as to reduce its diameter from the diameter atthe orifice 24 to the final diameter. Because of the surface tension andviscosity of the glass even at elevated temperatures, it is impracticalto make the orifices 24 of diameters even approximating the finisheddiameters of the fiber to be formed. They must, therefore, be many timesas large and each fiber is formed off a molten cone of glass extrudedthrough its particular orifice 24 by centrifugal force.

In order to control the rate of heat loss by the fibers during theattenuating length the apparatus and method the invention provide meansfor adding supplemental or auxiliary heat to the attenuating lengths ofthe fibers. In Fig. 1 this means is illustrated as a radiant burnergenerally indicated at 28 so positioned as to direct radiant energy atthe attenuating lengths of the fibers. In Fig. 1 the radiant burner orheater 28 is illustrated as comprising a ceramic ring 29 mounted in asupport ring 3% and provided with a plurality of gas inlet pipes 31 sothat the gas burns adjacent the curved radiating surface of the ceramicring 29. The gas flame is'short and hot so that it heats the radiatingceramic ring 29 and, by the high emissivity of the ceramic, radiantenergy is emitted from. the burner 28 toward the periphery 18 of thecentrifuge 17 and attenuating lengths of the streams 27 to be formedinto elongated fine fibers 32.

In the apparatus as illustrated in Fig. l a vertical column or enclosure33 extends downwardly beneath the centrifuge 17 in order to enclose thedescending shroud or veil of fibers 34 as they are carried downwardly bythe combination of gravity and the jet of air 25. A foraminous conveyor35 is shown as moving across beneath the enclosure 33 for accumulatingthe mass of fibers thereon in the form of a blanket 36 carried away bythe conveyor 35 and between compression rollers generally indicated at37. A suction box 38 may be located beneath the conveyor 35 to assist inlaying the fibers 32 of the veil 34downwardly on the conveyor 35.

In Fig. 2 a modified form of heat transferring means is shown fortransferring energy to apply heat to the attenuating lengths of glassstreams 39 that are being emitted from stream forming orifices 40 in theperiphery. of a rotary centrifuge generally indicated at 41. As in theembodiment of the invention illustrated. in Fig. 1, the centrifuge 41may be provided with a glass distributing basket 42 into which a streamof molten glass 43 flows. The glass in the stream 43 is distributed overthe inner face of the distributing basket 42 by centrifugal force andemitted as coarse streams 44 which impinge upon the inner surface of thecentrifuge 41. The streams 39, projected outwardly through theirorifices 4%) by centrifugal force, are entrained in a downwardly movingradial blast of gas 45 which is directed parallel to and concentric withthe axis of rotation of the centrifuge 41. The blast of gas 45 isdischarged from an. annular blower ring 46. As explained above, theblast of gas 45 may be air or steam at relatively low temperaturecompared to the temperature of the molten glass forming the streams 39.

The force of the blast 45 turns the streams downwardly redirecting themto form a generally tubular veil of fibers 47 and to move the veildownwardly away from the centrifuge 41.

In order to provide for effective attenuation of the streams 39 intolong, fine fibers 47, a supplemental heating means 48 is provided. Theheating means 48 consists of an annular ring 49 of ceramic, or othermaterial having a high rate of emissivity, so positioned, shaped anddirected as to concentrate the radiant heat energy upon the attenuatinglengths of streams 39 between their discharge from the stream formingorifices 40 and the ultimate reduction in diameter when they change fromsoftened attenuable streams to fixed diameter fibers. A plurality ofelectric coils 50 is positioned in the concave face of the radiant ring49 for generating the heat which is radiated from the heating means 48.The rings 50 are electrically connected to power input lines 51.

While the embodiments of the invention illustrated in Figs. 1 and 2employ radiant heat energy emanating from a source external of the veilof fibers 34 or 47, respectively, the invention also contemplates thetransfer of energy from a supplemental source external of the veil andexternal of the blast but in a form other than radiant heat.

The embodiment of the invention illustrated in Fig. 3 is similar to thatshown in Figs. 1 and 2 except for variation in the precise configurationof a centrifuge 52 and in the nature of the supplemental heat source generally indicated at 53. In Fig. 3 the centrifuge 52 has a frusto-conicalperiphery 54 with a taper that is inverted compared to the taper of theperiphery of the centrifuge 41 of Fig. 2. Like the earlier embodimentsof the invention, the centrifuge 52 may be provided with a glassdistributing basket 55 serving to distribute a molten glass stream 56 inthe form of coarse streams 57 to the interior surface of the periphery54 whence the glass flows through stream forming orifices 58 as glassstreams 59. The streams 59 are entrained in a blast of gases 60discharged from an annular blower ring 61 and attenuated to form fibers62 in a generally tubular, downwardly moving veil of fibers.

Supplemental heat is generated in the attenuating lengths of the streams59 by means of induction heating coils 63 carried by a frusto-conicalmounting plate 64.

Because of the chemical constituents of the glasses" known in the artand suitable for centrifugal fiber forming procedures, such glassesusually containing considerable proportions of alkali, the electricalcharacteristics of the glass streams 59 are such that the inductionfield created by the induction coils 63 generates heat within the bodiesof the streams 59 at their attenuating lengths.

In the embodiments of the invention illustrated in Figs. 1, 2 and 3, theblasts of gases 25, 45 and 60 are emitted from blower rings 26, 46 or61, respectively,

which are located at levels above the peripheries of the centrifuges 17,41 and 52, respectively. In these figures the attenuating blasts are sodirected as to impinge upon the streams 27, 39 or 59 at theirattenuating lengths to apply traction to the streams as they cool forattenuating them into fine fibers.

In the embodiment of the invention illustrated in Fig. 4 attenuation ofglass streams 65 to form fine fibers 66 is accomplished by transferringthe attenuating force along the fibers 66 back to the attenuatinglengths of the streams 65. In this embodiment of the invention acentrifuge 67, similar to the earlier described centrifuges and, ifdesired, having a glass distributor basket 68, has a generally annularperiphery 69 through which a plurality of stream forming orifices 70 aredrilled. A stream of molten glass 71 is flowed into the distributingbasket 68 and through its orifices 72 discharged as coarse streams 73onto the interior of the periphery 69 of the centrifuge 67. Centrifugalforce then flows the glass through the stream forming orifices 70 asstreams 65. The decrease in temperature of the glass streams 65 in theirattenuating lengths produces the fibers 66 of sulficient mechanicalintegrity to be entrained in an annular, downwardly moving blastgenerally indicated at 74 which is emitted from an annular blower 75located at a level below the stream forming orifices 70 of thecentrifuge 67. The blower 75 has a downwardly extending skirt 76 and theorifice of the blower 75 is so designed that the blast 74 hugs thesurface of the skirt 76, entraining and carrying the fibers 66downwardly therewith.

In this embodiment of the invention supplemental heat is transferred tothe attenuating lengths of the stream 65 to reduce their rate of heatloss from an annular radiant heat source generally indicated at 77 andcomprising a radiant emitting ring 78 heated by gas flames burning inports 79 fed from a gas line 80.

By employing a supplemental heat source to retard the rate of heat lossfrom the glass streams issuing from the centrifuge and an attenuatingblast emitted from a separate source, better control of the fiberforming process is made possible. The amount of supplemental heatsupplied from the external source is completely independent of theblast. In contrast, where a blast is relied upon for both force andsupplemental heat, a change in either force or heat of the blast alsoaffects the other.

In all or" the embodiments shown in Figs. 1-4 inclusive, thesupplemental heat not only is applied to or generated 7 in theattenuating lengths" of the glass streams but it also is effective atleast on the peripheral area of the centrifuges as well. The heat orenergy transferring means which surround the centrifuges are all capableof transferring the energy through the blasts of gas to the streams andto the centrifuges themselves. Radiant heat strikes the outer surfacesof the centrifuges 17, 41 and 67 of Figs. 1, 2, and 4 respectively. InFig. 3 the inductive field from the coil 63 encompasses the centrifuge52 as well as the streams 59. Thus in all four figures heat is alsoapplied to the centrifuges for retarding their loss of heat as well asretarding the loss of heat from the streams.

The embodiment of the invention illustrated in Fig. 5 comprises acentrifuging basket 81 into which there is fed a stream of molten glass82. The molten glass is spread over the inner surface of the basket 81and projected as streams 83 from orifices 84 into the path of a blast ofgases 85 from an annular blower 86. In this embodiment, supplementalheat is generated in the attenuating lengths of the streams bydi-electric heating. The centrifuge 81 is connected as one plate of asystem also including an annular plate 87 exterior of the blast 85 andboth are connected to a high frequency electrical generator 88.

As used in the following claims the phrases electrical energy field orelectrical energy apparatus" are intended to include, respectively,fields of electrical energy produced by both electromagnetic orinduction apparatus and capacitive or di-electric apparatus andapparatus of either type.

I claim:

1. In a method for attenuating fibers from streams of glass beingprojected radially outward from a centrifuge into an annular blast ofgas having high kinetic energy and that is moving generally parallel andconcentrio to the axis of the centrifuge for attenuating said streamsinto fibers and for redirecting said fibers as a generally tubular veilmoving longitudinally of such axis, the improvement comprisingtransferring energy inwardly through said blast from a supplementalsource other than said blast and external of said moving veil and saidblast to supply heat to the attenuating lengths of all of said streamsin sufiicient quantity for retarding the rate of heat loss therefrom butnot in suflicient quantity for increasing the temperature thereof.

2. A method for attenuating fibers from streams of glass being projectedradially outward from a centrifuge, said method comprising directing anannular blast of gas generally parallel and concentric to the axis ofthe centrifuge for attenuating said streams into fibers and redirectingsaid fibers as a generally tubular veil" moving longitudinally of suchaxis, and transferring radiant heat inwardly through said blast from asupplemental source external of and substantially surrounding saidmoving veil in sufiicient quantity for retarding the rate of heat lossfrom the attenuating lengths of all of said streams.

3. A method for attenuating long fine fibers from streams of glass beingprojected horizontally radially outward from a centrifuge, said methodcomprising, directing an annular blast of gas having a temperature lessthan the temperature of said streams downwardly across the paths ofmovement of said streams away from said centrifuge for entraining andattenuating said streams into fibers and for carrying said fibersdownwardly as a generally tubular veil, and applying heat inwardlythrough said blast from a source radially external thereof to theattenuating lengths of all of said streams in quantities sufficient forretarding the rate of heat loss from said streams in said attenuatinglengths but not sufficient for increasing the temperature thereof.

4. A method according to claim 3 in which the heat is applied bydirecting radiant heat inwardly through said blast onto the attenuatinglengths of said streams.

5. Apparatus for attenuating fibers from streams of heat softenablematerial being projected radially outward from the periphery of acentrifuge comprising an annular blower concentric with the axis of thecentrifuge and having an annular orifice for emitting a blast of gasesfor attenuating said streams into fibers and redirecting said fibers asa generally tubular veil moving axially away from said centrifuge, andan annular radiant energy source mounted radially external of saidmoving veil and of said blower and having its energy emitting meansdirected inwardly toward the periphery of said centrifuge for applyingsupplemental heat to the attenuating lengths of said streams.

6. A method for attenuating fine fibers from streams of glass that areprojected outwardly by centrifugal force from orifices in the peripheryof a centrifuge, said method comprising directing an annular highvelocity blast of gaseous medium generally parallel to and concentricwith the axis of said centrifuge for applying kinetic energy to saidstreams for redirecting said streams as a generally tubular veil movinglongitudinally of said axis and for attenuating said streams intofibers, and creating an electrical energy field from a source radiallyexternal of said blast, said field encompassing the periphery of saidcentrifuge and the attenuating lengths of said streams and havingsufiicient strength for generating heat in and retarding the rate ofheat loss from the attenuating lengths of said streams.

7. A method according to claim 6 in which the elec trical field iscapacitive.

8. Apparatus for attenuating fine fibers from streams of glass that areprojected outwardly by centrifugal force from orifices in the peripheryof a centrifuge, said apparatus comprising an annular blower concentricwith said centrifuge and closely spaced radially thereof for directing ahigh velocity blast of gaseous medium generally parallel to andconcentric with the axis of said centrifuge for applying kinetic energyto said streams for redirecting said streams as a generally tubular veilmoving longitudinally of the axis of said centrifuge and for attenuatingsaid streams into fibers, an annular radiant energy apparatus concentricwith and spaced radially externally of said annular blower and means forenergizing said apparatus for creating an energy field encompassing theperiphery of said centrifuge and the attenuating lengths of said streamsfor generating heat therein sufficient for retarding the rate of heatloss therefrom but not sufiicient for increasing the temperaturethereof.

9. Apparatus according to claim 5 in which the annular radiant energysource is a radiant heater.

(References on following page) References Cited in the file of thispatent UNITED STATES PATENTS FOREIGN PATENTS 7 France July 2, 1956(Corresponding to Belgian Pat. No. 545,632.) France Dec. 28-, 1936 GreatBritain Dec. 13, 1939 OTHER REFERENCES Abstract of Belgian Patent No.545,632, found in Recueil des Brevets dInvention, 1956, vol. 2, page252.

